How do aircraft interact with their environment? What interactions occur between airports and the environment? How do those interactions vary geographically and with time? Answering such questions is central to understanding aviation environmental impacts. In particular, two aspects of the relationship between air transport and the environment are important in understanding current debates: (a) the emissions from aircraft and airport infrastructure; and (b) the growth in demand for air transport. Those two themes – aviation emissions and aviation growth – recur throughout the subsequent chapters of this book, and understanding the issues associated with each is vital for a balanced view of the environmental impacts of air transport. Explaining the main trends in aviation emissions and growth is the focus of this chapter. Aircraft and airports have many interactions with the environment, by far the most important of which are the emissions generated by aircraft during their operation. This is not to imply that other environmental interactions are negligible. The materials and energy used in manufacturing, maintaining and ultimately disposing of aviation infrastructure – over the life cycle of that infrastructure – may be substantial and should be considered in aviation environmental impact assessments, especially in the case of airport infrastructure development. In addition, many environmental interactions occur during the surface transport of employees, passengers, freight, goods and waste to, from and within airport sites, and during the servicing of aircraft before and after flights. At the local scale, such interactions may result in significant, cumulative environmental impacts because major airports are sites of intensive resource consumption and waste production. Nevertheless, at the global scale – and increasingly at the scale of individual airports – the impact of aircraft emissions far outweighs any other aviation environmental effect in its magnitude and significance (Bows et al. 2009; Upham 2003). Therefore, an understanding of aircraft emissions is crucial to any discussion of aviation environmental impacts. Furthermore, despite some impressive technological and operational advances in the efficiency of air transport operations, absolute aircraft emissions are increasing – and are projected to continue to rise – due to the growth in demand for air

transport. This makes an understanding of the trends in aviation growth critical for a full understanding of aviation environmental impacts.